1. Field of the Invention
The present invention pertains generally to accessories for use on power drills and more specifically, to an accessory apparatus that may be readily attached to a power drill over a drill bit connected therein for providing additional capabilities such as screw driver and wrench-type functions.
2. Prior Art
Attaching an accessory onto the drill bit end of a power drill to provide additional functions such as screwdriving and the like is not per se new. In this respect the most relevant prior art known to the applicant herein is U.S. Pat. No. 3,484,114 to Rodin. Rodin describes the problems solved by such devices wherein he explains that a worker had previously used one power tool to drill a screw-receiving opening then put down the tool and used another power tool or hand tool to drive and install the screw in the opening. Still another power or hand tool must then be used if the screw-receiving opening must be counter-bored. The Rodin patent disclosure illustrates a device which solves this problem by providing an attachment for a power tool which enables a single power tool to be used to drill a screw-receiving opening and to install a screw in the opening. More specifically, Rodin describes an attachment which fits directly over the drill bit of a power drill and which carries a screw-driving blade at its forward end which is driven by the power tool to install the screw.
Unfortunately the Rodin patent disclosure describes a device which while solving the aforementioned problem of using separate tools to drill the hole and then insert the screw, the manner in which the Rodin attachment is secured to the power tool and the fact that there is no non-rotating portion of his attachment once it is so secured and the power tool is activated, renders the Rodin attachment relatively unsatisfactory from the standpoint of safety. One of the safety problems associated with this prior art device stems from the fact that connection of this attachment to the power tool depends upon the use of at least one pin the position of which is controlled by an externally exposed spring which is in a constant state of tension and which is rotated at a high rate of speed along with the attachment. A structural failure of the spring is entirely plausible in view of the repeated movement of the spring due to the interaction between the spring and the connecting pins. Such a failure could result in a release of the spring in which one or more portions of it, depending upon the nature of the failure thereof, could be whirled at high speed in a radial direction from the attachment and readily injure the user. Another safety problem associated with the aforementioned prior art is the fact that the entire attachment, including all external surfaces thereof, rotate with rotation of the power tool chuck. Consequently, the user cannot steady the screwdriver or other such tool within the attachment while it is being used. Any attempt by the user to grasp the exterior surface of the attachment, which is an entirely natural tendency to align the attachment with a screw for example, could seriously injure the user such as by a friction burn of the fingers or a fracture or break of bones in the hand or wrist or by a complete loss of control of the power tool which could result in even more serious injury.
Still another safety concern in regard to the Rodin disclosure relates to dimensional tolerances. More specifically, the Rodin attachment apparatus does not allow for variations in the diameter of the chuck and a slightly smaller chuck diamter could permit inadvertent and hazardous separation of the apparatus from the power tool.
There is therefore still a need to provide an attachment of the type previously described, but which overcomes the aforementioned safety disadvantages thereof while retaining the essential convenience of being able to use a power tool attachment such as for driving screws and the like which may be inserted over the drill bit of a power drill or comparable portions of similar power tools.